Safety control system for fuel burners



Oct. 13, 1953 G. G. oUTTERsoN 2,655,207

SAFETY CONTROL SYSTEM FOR FUEL BURNERS INVENTOR. G20/P615 G Z/TZ/PSO/V Oct. 13, 1953 G G, OUTTERSON 2,655,207

SAFETY CONTROL SYSTEM FOR FUEL BURNERS Filed May 5, 1949 4 Sheets-Sheet 2 Ti :1.7. T5 l INVENTOR.

620/962 G @Ufff/@SON Oct. 13, 1953 G. G. ouTTERsoN SAFETY CONTROL SYSTEM FOR FUEL BURNERS 4 Sheets-Sheet 5 Filed May 5, 1949 Y Tmr INVENTOR. 620/1955 G 00775950 W ff 4770A:

Oct. 13, 1953 G. G. oUTTERsoN SAFETY CONTROL. SYSTEM FOR FUEL BURNERS 4 Sheets-Sheet 4 Filed May 5, 1949 Patented Oct. 13, 1953 UNITED STATES PATENT OFFICE SAFETY CONTROL SYSTEM FOR FUEL BURN ERS George G. Outterson, Mexico, N. Y. Application May 5, 1949. seal No. 91,500

9 Claims. 1

The 'present invention relates to control or programming systems for producing sequential operation of a plurality of elements of a device or of a plurality of devices, such as oil or gas burners commonly used in household or commercial heating installations, steam generating plants, and the like. It relates more particularly to control systems for producing a predetermined cycle of operations for setting into operation and controlling the operation of fuel burners, and to safety control mechanisms for assuring proper and safe operation of such fuel burners.

A `fuel burner of the type referred to generally above, such as an oil burner, includes a device, such as pump or gravity feed system, for supplying the fuel oil to a combustion zone; a blower for supplying air to -support combustion of the fuel; and a device for igniting the fuel. The usual control systems for such oil burners include a thermostat or a pressure limit switch or other pres- :sure or temperature responsive device which is `lused to start and stop or otherwise regulate the :fuel burner. In addition, such systems include a :flame detector for determining whether the burn- 'er is operating properly. Many of these prior de- `vices, however, are not entirely dependable and fit often happens that when the igniting device is actuated and the flame is not detected, or when 'the flame is extinguished, the fuel and air supjply means may continue to operate for a period of time before their operation is discontinued, thereby discharging an explosive air-fuel mixture finto the combustion chamber. Subsequent opera- :tion of the igniting device may ignite this highly combustible mixture causing it to explode within `the combustion chamber and/or the flues with .resulting damage to the heating system.

By virtue of the applicants novel switching arrangement, a control system is provided ln which the failure of any one of the components to function prohibits continued operation of the system :and assures, thereby, a safe programming se- Aquence. The arrangement avoids a multiple connection of the igniting means and the fuel valve, for example, to a common power terminal, in this lmanner overcoming a serious defect present in the prior art. Heretofore, due to such a common circuit connection, the failure of a single element to function usually did not effect the subsequent operation of the remaining element .or elements.

v The present invention has, therefore, as a principal object, the provision of a control system whereby danger of explosion of air and fuel mix'- tures is overcome.

AHM-her Object Of the invention ,is to provide s control system for fuel burners whereby positive control of the sequence of operations of the blower, fuel supply means and igniting device is ob tained and wherein the combustible mixture of air and fuel is purged from the combustion chamber before the igniting device is set into operation.

A Yfurther object of the invention is to provide a control system for fuel burners wherein 'failure of the fuel to ignite will shut off the flow of fuel to the system and will purge the combustion chamber of combustible fuel and air mixtures before the igniting device and the fuel supply means are again set into operation.

More particularly, it is an 'object of the invention to provide a timer cam for delaying the flow of the fuel to the combustion chamber and the ignition thereof until after the air supplying means, such as a blower, has operated for a predetermined period of time sufficient to purge the system of combustible mixtures of air and fuel or until the blower builds up air pressure to a desired level.

It is a further object of the invention to provide a control means which assures the discontinuance of operation of the fuel supplying means if the fuel is not ignited within a short period of time after the supplying means is set into operation and which assures proper repetition of the above-described cycle so long as the system opcrates properly, but which makes it necessary to reset the system manually in the event of failure of any of the elements of the system.

Still a further object of the invention is to provide a control in which the whole system is automatically rendered inoperative upon failure of any part of it to function properly.

A further and more general object of the invention is to provide a control system which is rendered safe when any of its component parts for the device controlled thereby fail to function properly.

Other objects of the invention will become apparent from the following description of typical systems embodying the present invention.

While systems of the type embodying the pres-v ent invention are useful for many different purposes in which a program or cycle lof operations is desired, the invention will be described as applied to a fuel burner in order to simplify the eX- planation of the system. Systems embodying the present invention may be provided with any conventional temperature or pressure responsive means for starting and stopping the operation of the fuel burner.

For a better understanding of the present invention, reference may be had to the accompanying drawings, in which:

Figure l is a schematic diagram of a typical control system for direct ignition oil-fired fuel burners, embodying the present invention;

Figure 2 is a schematic diagram of a typical control system for pilot ignition oil-fired fuel burners, embodying the present invention;

Figure 3 is a schematic diagram of a safety device used in the systems of Figure 1 and Figure 2 for assuring their proper operation;

Figure 4 is a perspective view of a timer cam assembly including a representation of an alternate safety device constructed in accordance with the present invention;

Figure 5 is a plan view of a second alternate safety device;

Figure 6 is a, View in side elevation of the safety device of Figure 5;

Figure '7 is a representation of the safety device of Figure 4 showing it in starting position;

Figure 8 is a representation of the safety device of Figure 4 showing it in operating position;

Figure 9 is a representation of the safety device of Figure 4 showing its position after flame failure;

Figure l is a, schematic diagram of a typical control system for pilot ignition gas-fired fuel burners, embodying the alternate safety device of Figure 4; and

Figure 1l is a schematic diagram of a typical control system for pilot ignition oil-fired fuel burners, embodying the safety device of Figures and 6 in an alternate arrangement.

As indicated above, the present invention comprises a system having control elements whereby a program or cycle of operations must be followed in setting a fuel burner into operation and controlling the operation of the fuel burner thereafter. A principal feature of the system -is the provision of a suitable timer cam switch which, in a typical embodiment, first sets the blower of the burner into operation to purge the system of combustible mixtures and after such mixtures have been purged supplies fuel for ignition by means of a suitable igniting device.

rihe system also includes elements whereby failure of the fuel to ignite will discontinue the operation of the fuel supplying means, the igniting device and the blower so that the system must be reset manually for repetition of the above cycle. Also, the system is provided with control elements so that, if the flame should be extinguished yduring normal operation, the entire system will stop and must be reset manually for proper operation.

The system is characterized by a relatively small number of control elements which are so inberff', which, for example, may be a pressure' controlled switch, aquastat or thermostat; a relay Ill yhaving a relay coil Iia, and normally open contacts Illia-Ifile, Idd-Ide; and a name detector mechanism FD which in a typical embxli-v A and conductor 35.

ment may include a metal helix actuated by heat, an electric eye or electric prober, or any device which will perform a switch operation as a result of the presence of flame in the burner. The ame detector FD controls a relay IE including a relay coil Ita, having associated therewith normally closed contacts itc-itc and normally open contacts IGd-IBe. The system also includes a timer motor TM controlling the operation of a timer cam assembly, to be more fully described hereinafter.

Fuel under pressure may be supplied by gravity, line pressure or by a pump P driven by an appropriate motor. A solenoid valve V is operated electrically to control the now of fuel to the burner. A blower B for the fuel burner may be driven by the same motor that drives the fuel pump P. The ignition of the combustible mixture is initiated by an igniting device I. The system also includes a safety circuit having a safety device S, to be more fully described hereinafter in connection with Figure 3.

The timer cam assembly includes the timer motor TM (shown in Figure l) which, through a. magnetic clutch 25, drives a gear train 2B in a stepdown arrangement, as shown in Figure 4. A shaft 2l is connected to the gear train 2t, and a spring 29 is suitably affixed thereto for returning the shaft to its original position at the completion ofthe programming cycle. Secured to shaft 2 is a cam Sii, the periphery of which is generally shaped into two contrasting curved portions of apiece. Switch SI, normally closed, and switch 32, normally open at the beginning of the cycle (also shown in Figure l), engage the peripheral portions of cam 39 and are periodically opened and closed during the rotation thereof. The timer cam assembly, shown in Figure 4, also includes an arm 3d which is secured to and extends laterally from shaft 2l, and which engages a stop 35', positioned on the frame 'I of the apparatus, at the beginning of the cycle.

instead of switches 3| and 32 which are the single-pole-double-throw or single-pole-singlethrow type, the latter being operated by moving the levers 3Ia and 32a, a switch can be used which when moved in the same direction alternately closes and opens. ln such type switches, the cam 3i! can be in the form of simple projections which operate first to move the switch to a closed position, and then to an open position. The word cam is used in its generic sense, to include any eccentrically arranged means on the shaft 2 to operate the switches 3l and 32 in the timed sequence, as explained.

Referring now to Figure 1, the system is connected to the power lines A+ and A- which supplies a suitable operating voltage. The power line A+, as illustrated, is connected to one contact of the switch I by a conductor 36, the other contact thereof is connected by means of conductor 3l to the primary winding 38 of transformer II and then to power line A- through conductor S9. The low voltage or initiating circuit through the secondary winding 40 of transformer II 'is completed by means of conductor 4I which connects to control member T, a conductor 42, contacts I Bb--Ic of relay I6, a conductor B3, safety circuit S, a conductor 44, relay coil Illa of relay I4,

Conductor 45 connects contact Ie of relay I4 to conductor 42 of the above circuit, and cooperating contact Md thereof connects to conductor 43 by means of conductor 46.

The power line A+ is also connected by means of conductor 41 to relay coil I6@ of relay I6 and thrcughconductor 48 tothe flame detector mechanism VFD. conductor 49 connecting the latter to power line A-, In addition, power line A+ is connected by means of conductor 50 to contact |4 of relay i4 which is normally spaced apart from cooperating contact |4b thereof, and through which is connected by conductor 5| to the fuel pump P which has the blower B associated therewith. Connected to conductor 5| is conductor 52, switch 3|, conductor 53, switch 32, conductor 54 and the fuel solenoid valve V, the latter connecting to power line A- through conductor 55. Igniting means I is connected to conductor 53 by means of conductor 56 and is connected to power line A- through conductor 51.

The timer motor TM is connected across conductor 5| and the power line A by means of conductors 58 and 59, respectively. The contact |6e f relay |6 is connected to conductor 5| by conductor 60, and cooperating contact |6d is connected to conductor 54 through conductor 6|.

Assume now that the Switch l0 is closed so that the above described system is an operative condition and the circuit is completed through the conductor 36, the switch 9, the conductor 31, the primary winding 38 of the transformer and the 'conductor 39 to the power line A-. Also assume that the burner is not in operation and that when the boiler pressure, water or room temperature reaches the desired lower value, the control member T calls for heat.

Further assume that the safety device S is not tripped, Hence, the initiating circuit is cornpleted through the secondary winding 4U of the transformer conductor 35, relay coil |4a of relay I4, conductor 44, heater coil 24 of safety device S, conductor 43, normally closed contacts I6c-|6b of relay I6, conductor 42, control member T and conductor 4|.

The closing of contacts |4c-|4b, which are holding contacts, permits current to now from power line A+ through conductor 50, conductor 5|, conductor 58, timer motor TM and conductor 59 to power line A, thereby initiating the operation of the timer motor TM. Simultaneously, a circuit is completed through conductor 5I, the pump P and blower motor B, also initiating their operation. Since switch 3|, at point on cam 30 of Figure 4, is normally closed, the igniting means I is energized through conductor 52, conductor 53, conductor 56 and conductor 51.

When timer motor TM operates, shaft 21 rotates in the direction shown by the arrow of Figure 4, at a fairly slow speed, such as one revolution per minute, for example. During the rst quarter revolution, switch 3| remains closed and switch 32 remains open, at the end of which time, however, switch 32 closes. When switch 32 closes, current hows from conductor 53 through conductor 54, the solenoid fuel valve V and conductor 55, thereby energizing the solenoid fuel valve V and permitting fuel to flow to the burner.

During the second quarter revolution, both switches 3| and 32 remain closed, and solenoid fuel valve V and igniting means I overlap in operation. When the fuel is lighted and flame is detected by the flame detector mechanism FD, a circuit is completed from power line A+ through conductor 41, relay coil ld of relay I6, conductor 48, flame detector FD and conductor 49 to power line A-. The normally open contacts iSd-Nie of relay I6 close, creating a circuit from conductor 5| through conductor 60, conductor 6|, conductor 54, solenoid fuel valve V to conductor l55, thereby shunting the original circuit thereto through switches 3| and 32. Thus, 3S long as llame is detected, fuel valve V can function. Also, when relay I6 is energized, contacts |5b|6c thereof open, a feature to be more fully described in connection with the operation of the safety system.

During the third quarter revolution, switch 3| opens, and switch 32 remains closed, thereby maintaining an electrical energizing path for the igniting means I from conductor 5| through conductor 50, contacts Edf-Hic, conductor 6|, switch 32, conductor 56, igniting means I and conductor 51. Thus, igniting means I remains energized for one quarter of a revolution after switch 3| opens, assuring continued ignition of the flame during this interval.

At the begining of the fourth quarter of revolution, switch 32 opens, disconnecting the circuit through the igniting means I. Simultaneously, extension 34 on shaft 21 engages a stop (not shown) on the frame of the apparatus, thereby maintaining switches 3| and 32 in an open position. The system then continues in operation as 1011s aS flame is detected by the flame detector FD which maintains contacts |6d|6e of relay |6 in a closed position and permits fuel to flow from fuel valve V.

When the heating requirements have been satisfied, as when the upper desired temperature is reached by control member T, the initiating circuit is disconnected thereby causing relay I4 to be rie-energized. As a result, contacts |4b-|4c, and idd-|46 thereof open, the former discon- 1 necting the circuit to the timer motor TM, the

solenoid fuel valve V, the pump P and the blower B. Since flame is no longer detected by the flame detector FD, relay l5 is fle-energized, and contacts 16d- |69 open and contacts |6c-|6b close. When the timer motor TM ceases operation, the spring 29 which has increased its tension through the rotation of shaft 21, is free to reset and shaft 21 returns to its original position by stop 35. Thus, switch 3| is again closed and switch 32 is again open.

One embodiment of a typical safety device S used in connection with the direct ignition oilfired system may consist of a conventional bimetallic warp switch having a heater coil 24 Wrapped therearound, the device (schematically shown in Figure 3) being suitably supported on an insulated base. The utilization of such a device in a safety circuit is disclosed in Figures 1 and 3 wherein relay i6 includes a normally open Contact lf which is connected by means of conductor 63 to conductor 44. Heater coil 25E is inserted in series with conductor 43 and conductor 44,

When the initiating circuit through relay coil lila of relay I4 is energized due to control membei' T calling for heat, current flows from the secondary winding D through conductor 35, relay coil 54a, the heater coil Effi in the warp switch of safety device S, conductor 3. and contacts |6c-|6l7 of relay i6, conductor c2, control. niember T to conductor 4|. Contacts Iff-c-|4b and. I4e|4d of relay Il. close, the latter creating a circuit through conductor 45 and conductor 6:5 which parallels the above described circuit through contacts ISC-|627 of relay i5.

When flame is detected, .relay coil |J of relay i3 is energized and contacts Ilich-|66 close, contacts [5c-|31) open, as described previously, and contacts |6b|t`f close, shunting heater coil 24 through conductor E3 and conductor 42.

. means of conductor 35.

l' If flame yis not detected within apre-selected period of time, however, the relay coil |6a of relay i6 does not become energized and the respective contacts thereof do not operate. If contacts isb-|31* do not close, current continues to ow in the low Voltage circuit through coil 2d, causing it to heat and separating the contacts thereof. Thus, the circuit is disconnected and relay coil Ila of relay I4 is de-energized and the system becomes inoperative. To restart the programming cycle, the switch associated with heater coil 2li must be manually reset.

If, for any reason, the flame goes out, after the system is operating, the flame detector FD disconnects the circuit through the relay |S and relay coil i3d is de-energized, opening contacts ic-ld thereof and shutting off the solenoid fuel Valve V. Blower B operates, however, to clear the combustion chamber of any explosive vapors that might be ignited by hot refractory therein until the safety circuit S, described above, commences operation, i. e., when contacts |6b|6f open and the heating coil 22 draws the current and disconnects the initiating circuit.

The system may also include a modulating (variable firing rate) regulator R circuit, as shown in Figure l. Conductor 35 connects the firing rate regulator R to switch t6, preferably a single-pole-single-throw switch cooperating with switch 32 which connects to the conductor di by means of conductor 3l. The other side of firing rate regulator R is connected to power line A- by conductor 68.

Before the flame is detected, current cannot reach firing-rate regulator R to openl the valve except through switch 3| and switch 32. When switch 32 is closed, the cooperating switch 5t is open and it is impossible for the firing rate regulator R to operate. Only after contacts idd and Ic of relay l close when flame is detected by flame detector FD and after switch 32 opens at the beginning of the fourth quarter of rotation of the cam 30, does switch 36 close and the firing rate regulator R operate. Thus, the system is in operation and the programming sequence is completed before the firing rate regulator R can function.

The modication disclosed in Figure 2 of the drawings, a pilot ignition oil-fired fuel system, is similar to the circuit of Figure l except that a pilot solenoid valve PV is included and the timer cam shaft 2 is rotated 90 counterclockwise from the initial position used with the direct ignition oil-fired system to provide an alternate programming sequence.

Referring to the circuit of Figure 2, contact ltd of relay l5 is connected by means of conductor i6 to switch 32, conductor il and junction lil. Lead 'I9 from junction i8 connects to the pilot solenoid valve PV and to the power line A- through conductor Eil; the lead 8| from junction lli connects to igniting means I and thence to power line A- by means of conductor 82. Contact Idd is also connected by a conductor 87 to switch gib, a single-pole-double-throw switch. Contact i-i of switch 3|b connects to conductor 5| through conductor fili, and contact 3|-2 thereof is connected to solenoid fuel valve V by Conductor B connects the solenoid fuel valve V to power line A-.

When the timer shaft 2l is rotated counterclockwise through the 90 angle, or 1/4 revolution, contact 3 I-l ofswitch SIb is in a normally closed position and, conversely, contact iii-2 thereof is normally open. Switch 32, a single-pole-single-throw switch is in a normally closed position.

The operation of the pilot ignition oil-fired system is similar in some respects with the circuit of Figure 1, i. e., the direct ignition oil-fired system. When the low Voltage or initiating circuit is energized by control member T calling for heat, as described previously, a circuit is completed after relay I4 is energized and contacts Mc--Idb thereof close from power supply A-I- through conductor 50, contacts idc-Mb,

conductor 5|, conductor 84, contacts 3|-I of Y At the beginning of the second quarter revolution, contact 3|| of switch 3|b opens, and contact 3|-2 closes. 'Ihe pilot dame having been detected by flame detector FD results in the energization of the circuit through relay I6. A circuit is completed from conductor 5|, conductor 60, contacts Ide-Nid of relay It, conductor 81, closed contact 3|-2, conductor 85, the solenoid fuel valve V, conductor 36 to power line A and the fuel is ignited. Contact 32 remains closed, providing an overlapping period of operation between the pilot solenoid valve PV and the igniting means I, and the fuel solenoid valve V.

At the beginning of the third quarter revolution, switch 32 opens and contact 3|-2 remains closed. Extension 34 on shaft 21 engages a stop (not shown) on Vthe frame of the apparatus, thereby maintaining the switches in these positionsV during normal operation. When the heating requirements have been satisfied, the circuit is returned to its original condition in the manner described in connection with Figure 1.

If for some reason the pilot light goes out during operation, relay coil Ita of relay IS is deenergized, causing contacts lfb- |60 thereof to close, and contacts ltd-16e to open. When contacts |6d|6e open, the circuit is disconnected to solenoid fuel valve V and fuel does not ow to the burner. Since switch 3 Ib is a singlepole-double-throw switch and the only source of energization is through contacts lSd-le'when contact 3 |-2 is closed, it is a mechanical impossibility to turn on solenoid fuel valve V if relay I6 is not operating.

The safety circuit, disclosed in Figure 3 and in the circuit of Figure 1 may also be included in the pilot-ignition oil-red system of Figure 2, operating as described above. Y

rlwo alternate modifications of safety devices are shown in Figures 4, 5 and 6. Referring now to Figures 5, and 6, a safety device comprising an electromagnetic coil is shown, which device actuates a switch IUI having actuating elements IMA and IUIB and a control arm |02 pivotally mounted thereon at |04. Switch member lill may be suitably affixed to a frame |69 upon which the housing 25a of the timer motor TM including the magnetic clutch 25 and the timer shaft 21 are also mounted. A supportV member |05 is bolted to frame |98 at |08 to position the coil of the safety device. Armature m3 of the coil I I I pivots in the flange and pin assembly, |09 and l II),l respectively, and may be irregu- 9 larly shaped to extend through an opening in frame |00, as best seen in Figures 5 and 6. This form of the safety device may be connected in the circuit as shown in Figure 11 as described more fully below.

The second alternate safety device is shown in Fig. 4, wherein relay coil |8a of relay I6 performs the same function as the above mentioned coil Armature |08 is adapted to be actuated by relay coil |6a simultaneously with movable contact |6b.

The operation of the safety device of Figure 4 may be best understood with reference to schematic Figures 7, 8 and 9, Figure '7 representing the starting condition, i. e., when flame has not been detected by the flame detector FD and relay coil 16a of relay I6 is not energized, as described in connection with the above systems.

In the starting position, extension 34 on timer shaft 21 is retained against stop 35' on framework by means of spring 29, and contacts Hic-|611 of relay i6 are closed. After flame is detected by the flame detector FD, relay i6 is energized, opening contacts |6c|8b thereof and closing contacts |6b|8g when armature |08 engages relay coil |6a.

During a normal programming sequence, as described above, the timer shaft 21 rotates until the system is in operation, at which time the extension 34 on the timer shaft 21 engages armature |08', as best illustrated in Figure 8.

In case of a flame failure, however, the relay I6 is not energized and armature A|08 remains in its original position. Since timer motor TM is operating, shaft 21 rotates permitting the extension 34 thereon to by-pass armature |08 and to trip angle arm |02 of switch |0| instead, thereby operating actuating element |0|Athere of to close the switch l0 l. Ajs switch |0| is placed in the circuit at any point which will control either directly or indirectly the timer motor TM, the solenoid fuel valve V, and the'igniting means I, the entire system is cie-energized. In order to restart the programming cycle, element |0|B of switch 0| must be manually reset. The modification disclosed in Figs. 5 and 6 functions in a manner quite similar to that of Fig. 4. In a normal programming sequence, coil is energized, thereby attracting armature |08, so that the extension of armature |08 protrudes through the opening in plate |00. 'I'he rotation of the timer shaft 21 brings extension 34 into engagement with the extension of armature |08.

In case of flame fai1ure,4extension 34 will bypass armature |08 and trip angle arm |02 of switch l 0|.

The modification disclosed inthe circuit of Figure 10, a pilotignition gas-fired system, is similar to that of Figure 2 except the alternate safety arrangement of Figures 4, 7, 8 and 9V is included. This form of the safety arrangement is controlled by the timer motor and does not appear as a separate component in the schematic of Fig. lo, other than as switch |0| which is operated by control 4arm |02 as disclosed in Fig. 6.

Switch |0i is placed in the power line A+ between conductor 41 and the junction of conductors 35 and 50. Timer shaft 21 is returned to the position indicated in Figures l and 4, i. e., so that contact 3|| of the single-pole-double-throw switch 3| is closed and switch 32 is open.

With reference to Figure l1, a modified form of the pilot ignition gas-fired system of Figure 10 is shown. Herein, however, switch member |0| is placed in line 5| between the junction of conductors 5| and 58 and contact |41; of relay I4, and safety device is connected by means of conductor |22 to one end of the secondary winding 40 of transformer and to contact IBg of relay I6 by means of conductor |2|. A schematic representation of the control member T is shown which includes a pivotally mounted bimetallic warp element arranged to make contact with conductor 42 and conductor i5 when heat is demanded.

The alternate pilot ignition gas-fired systems disclosed in Figures 10 and 1l produce a similar sequence of operations to that described in connection with the system of Figure 2. In this circuit, however, blower B operates upon the actuation of kthe initiating circuit, as before, but for one quarter of a revolution before the pilotignition circuit is energized, thereby purging the system of any combustible matter that may have remained therein from the proceeding operation.

At the beginning of the second quarter of revolution, switch 32 closes and the circuit through the pilot-ignition meansis completed from conductor -5| through conductor 84, contact 3|| of switch 3|, conductor 8'! and conductor 16 to conductor 82. Flame is detected by the ame detector FD and relay I6 is energized, as before, and another circuit is created to the pilot-ignition means through conductor 16l from conductor 5| through conductor 60 and contacts IBe-ld of relay I6.

At the beginning of the third quarter of revolution, contact 3|-2 of switch 3| closes, completing the circuit to the solenoid fuel valve V. Switch 32 remains closed during this interval asa safety measure, and at the beginning of the fourth'quarter of revolution opens, contact 3|-2 of switch 3i remaining closed, and the programming cycle is completed.

The reset mechanism and safety device function in the manner described and only through the simultaneous failure of the flame detector FD circuit, switch |'0-', andI safety device, a condition which is extremely unlikely to occur, can the system fail.

From they preceding description of typical forms ofif'uel burner control systems, embodying the invention, it will be clear that a system is provided wherein va positive sequence of operations, assuring safe functioning of the fuel burner, is assured under all normal conditions of operation. The' system is susceptible of considerable' lchangel in the type of heating device controlled thereby, the type of flame detector used therein and the'l timer assembly used for timing the sequence of operations. For example, instead of a timer cam 3f! of the type described above, ,a plurality of separate cams may be used, each controlling an individual switch, and timer motor TM may be placed, forv example, in the' low voltage` or initiating circuit. Thus,.the systemsv described above take` care of all eventualities and assure proper functioning and safety of a burner and heating system.

It will be understood further that elements of the system can be combined, for example, the relay i6 may be an integral part of the flame detector mechanism FD. Therefore the forms of the invention described above should be considered as illustrative of the invention and not as limiting the scope of the following claims.

I claim:

1. A programming device for fuel burners comprising, in combination, a source of power, a first circuit connected across said source of power including a first switching means, a second switching means and an electrically operable fuel burning ignition means, said first and second switching means being closed during ignition, a second circuit shunting said second switching means and said ignition means and including a third switching means and a fuel supplying means, said third switching means being open when said first switching means is closed, means for operating said first, second and third switching means in timed relation to energize said ignition means and said fuel supplying means, a third circuit shunting said first switching means, said third circuit including a fourth switching means, said fourth switching means being normally open, and means responsive to combustion produced by said ignition means for closing said fourth switching means.

2. A programming device'for fuel burners as set forth in claim 1 including fth switching means connected in series with said rst and second circuits and means for closing said fifth switching means to start the system and for opening the .same to shut down the system.

3. In a programming device for fuel burners as set forth in claim 2 said means for opening and closing said fifth switching means including a low voltage control circuit comprising a thermostat, a thermal time delay switch and a relay coil, said fifth switch means being actuated by said relay coil to a closed position on completion of the low voltage control circuit.

4. In a programming device as set forth in claim 2 including a normally closed sixth switching means connected in series with said first and second circuits and said fifth switching means, said means for operating said rst, second and third switching means in timed relation including a timer motor, and operative driving connections between said timing. motor and the sixth switching means for opening said sixth switching means upon ignition failure.

5. In a programming device as set forth in claim 4 including a safety device comprising electromagnetic means for stopping said timer motor during normal combustion before it operates said sixth switching means, and means connecting said electromagnetic means so as to stop said motor upon response of the combustion responsive means.

6. A fuel burner control system having electrically operable fuel burning ignition means and fuel supplying means comprising a source of power, a first circuit across said power source including rst and second switch means and said ignition means in series, said second switch means being closed during the entire ignition period, a second circuit shunting said second switch means and said ignition means including a third switch means and said fuel supplying means, said third switch means adapted to 4be closed when said first switch means is open, a timing motor, cam means-driven by said'timing motor for controlling said first, second Vand third switch means in timed relationship to operate said ignition means and fuel supplying means, a'third circuit shunting said first switch means including a fourth switchmeans, and means responsive to combustion produced by said ignition means for closing said fourth switch means.

7. In a programming device for fuel burners as set forth in claim 6 including extension means driven by said timing motor simultaneously with said cam means, a-link carried by said fourth switch means for cooperative action with said extension means when said fourth switching means is in one position of operation for stopping the movement of said timing motor and cam means prior to completion ofthe control cycle thereof.

8. In a programming device for fuel burners l as set forth in claim 7 including normally closed fifth switch means connected in series with said source of power for opening the circuit to said ignition means and said fuel supplying means, said fifth switch means having means adapted to be engaged by said extension means for opening said fifth switch means in the event said extension means is not engaged by said third switch means.

9. In a programming device for fuel burners comprising the combination as set forth in claim 6 and including a shaft driven by said timing motor for carrying said cam means, an extension arm carried by said shaft, armature means responsive to energization of said means responsive to combustion, said armature being adapted to be pulled into the path of movement of said arm to block the movement of said drive shaft and terminate the movement of said cam means, and a fifth switch means interposed in the path of movement of said arm 'beyond the angular position of said armature in the direction of shaft rotation, said fth switch means being adapted upon being engaged by said arm to disconnect said source of power from said igniting and fuel supplying means.

GEORGE G. OUTTERSON.

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